PROJECT ABSTRACT This is an application to renew the Infectious Diseases/Basic Microbial Pathogenesis Training Grant from Washington University. With the advent of generally available antibiotic therapy about 50 years ago, many physicians and scientists predicted the end of infectious diseases as a major area of health concern. Subsequent events have proven this prediction wrong, and the past decades have seen the emergence of many newly identified infectious diseases, including Lyme Disease, erlichiosis, SARS, West Nile encephalitis, chikungunya, MERS, ebola and HIV. The reemergence of old infectious diseases, such as malaria and tuberculosis, in more virulent and more antibiotic resistant forms also has increased public attention on the health problems posed by infectious diseases. It is rare that a week goes by without some troubling headline concerning new infectious disease outbreaks. Thus, far from gradual disappearance as a health concern, infectious diseases have emerged as being of increasing importance to the health concerns of the nation. The emerging antibiotic resistance of current pathogens and the rise of new disease agents have made clear the necessity of increased fundamental scientific investigation into all aspects of infectious diseases. The purpose of the Washington University Training Program in Infectious Diseases/Basic Microbial Pathogenesis is to help fulfill this need by recruiting promising young investigators to this field and training them in outstanding research programs with preeminent investigators who collaborate across multiple disciplines (or who function in interdisciplinary teams) to perform infectious disease research. Our Training Program, which has had NIH support for the past 35 years, integrates faculty from four departments: Medicine, Pediatrics, Molecular Microbiology and Pathology & Immunology. The program provides training to M.D., Ph.D., and M.D./Ph.D. postdoctoral fellows, and to Ph.D. and M.D./Ph.D. students, in disciplines related to pathogenesis and host defense in Infectious Diseases. The laboratories of the program preceptors use tools of molecular biology, biochemistry, genetics, genomics, immunology, cell biology and translational medicine. Thus, the program trains young investigators to be able to answer the important questions of microbial pathogenesis, from studies of basic biology through application to the bedside.